The present invention is directed to heterocyclic compounds comprising dihydropyridines having alkyl and cycloalkyl moieties connected to the 4-position of the pyridine ring. More particularly, the invention is directed to NPY antagonist of alkyl and cycloalkyl derivatives of 1,4-dihydropyridine.
Neuropeptide Y (NPY) is a 36 amino acid peptide first isolated in 1982 from porcine brain. The peptide is a member of a larger peptide family which also includes peptide YY (PYY), pancreatic peptide (PP), and the non-mammalian fish pancreatic peptide Y (PY). Neuropeptide Y is very highly conserved in a variety of animal, reptile and fish species. It is found in many central and peripheral sympathetic neutrons and is the most abundant peptide observed in the mammalian brain. In the brain, NPY is found most abundantly in limbic regions. The peptide has been found to elicit a number of physiological responses including appetite stimulation, anxiolysis, hypertension, and the regulation of coronary tone.
Structure-activity studies with a variety of peptide analogs (fragments, alanine replacements, point mutations, and internal deletion/cyclized derivatives) suggest a number of receptor subtypes exist for NPY. These currently include the Y1, Y2, Y3, and the Y1-like or Y4 subtypes.
Although a number of specific peptidic antagonists have been identified for most of the subtypes, few selective non-peptidic antagonists have been reported to date. The heterocyclic guanidine derivative He 90481 (4) was found to be a weak but competitive antagonist of NPY-induced Ca++ entry in HEL cells (pA2=4.43). The compound was also found to have xcex12-adrenergic and histaminergic activity at this dose range. D-Myo-inositol-1,2,6-triphosphate was reported to be a potent but non-competitive antagonist to NPY-induced contractions in guinea pig basilar artery. Similarly, the benextramine-like bisguanidines were reported to displace 3H-NPY in rat brain (IC50, 19 and 18.4 xcexcM) and to display functional antagonism in rat femoral artery. The bisguanidine was shown to be functionally selective for the Y2 receptor since it antagonized the effect of the NPY2 agonist NPY13-36 but had no effect on the vasoconstrictive activity of the NPY1 agonist [Leu31, Pro34]NPY as disclosed in J. Med. Chem., 1994, 37, 2242-48, C. Chauraisia, et al.
Compound BIBP 3226, as reported in K. Rudolf, et al., Eur. J. Pharmacol., 1994, 271, R11-R13, displaces I-125 Bolton-Hunter labeled NPY in human neuroblastoma cells (SK-N-MC). BIBP antagonized the NPY-induced increase in intracellular Ca++ in SK-N-MC cells as well as antagonizing the NPY-induced pressor response in pithed rat experiments.
In addition to displacing I-125 labeled NPY and PYY in human neuroblastoma cells, compound SR 120819A, as reported in C. Serradeil-LeGal, et al., FEBS Lett., 1995, 362, 192-A6, also antagonized NPY-related increases in diastolic blood pressure in an anesthetized guinea pig model.
Over the past two decades, extensive work has been conducted relating to the 4-aryl-1,4-dihydropyridine class of compounds. Syntheses of compounds in this category have been driven by their pharmacological actions involving calcium channels rendering them useful for treating cardiovascular disorders such as ischemia and hypertension.
Numerous prior patents and publications disclose various dihydropyridine derivatives. One example is U.S. Pat. No. 4,829,076 to Szilagyi, et al. disclosing compounds of formula (1) as calcium antagonists for treating hypertension. 
U.S. Pat. No. 5,635,503 to Poindexter, et al. discloses 4-(3-substituted-phenyl)-1,4-dihydropyridine derivatives having NPY antagonist properties. These derivatives conform to structural formula (2). 
In (2), B is either a covalent bond or the group xe2x80x94NHxe2x80x94. The symbol Z denotes hetaryl moieties, examples being homopiperazinyl or piperazine.
U.S. Pat. No. 5,554,621 discloses related derivatives where Z is a fused ring or a spiro-fused nitrogen heterocycle. U.S. Pat. No. 5,668,151 also discloses related derivatives where Z is a piperidinyl or tetrahydropyrindinyl.
U.S. Pat. No. 6,001,836 to Poindexter, et al. discloses cyanoguanidine derivatives (3) of the 4-(3-substituted-phenyl)-1,4-dihydropyridines having NPY antagonist properties. 
The above-noted compounds have shown to posses antagonist activity. However, there is a continuing need for dihydropyridine derivatives having improved NPY antagonist activity.
The present invention is directed to novel dihydropyridine derivatives having NPY antagonist activity. More particularly, the invention is directed to alkyl and cycloalkyl derivatives of dihydropyridines.
Another aspect of the invention is to provide dihydropyridine derivatives that are effective in promoting weight loss and treating certain disorders in a mammal by administering to the mammal an anorexiant effective dose of an active compound of the invention.
A further aspect of the invention is to provide a method of treating clinical disorders amenable to alleviation by eliciting an NPYY1 response by administering to a patient an effective amount of a compound of the invention.
Another aspect of the invention is to provide a pharmaceutical composition for use in promoting weight loss and treating eating disorders, where the composition comprises an anorexiant effective amount of an active compound of the invention and a pharmaceutically acceptable carrier.
The compounds of the invention have the Formula I and its pharmaceutically acceptable acid addition salts or hydrates thereof 
wherein
R1 and R4 are independently selected from lower alkyl and CO2R5, cyano and 
xe2x80x83where R5 is a lower alkyl;
R2 and R3 are independently selected from hydrogen, cyano and lower alkyl;
A is an alkyl or cycloalkyl;
n is an integer selected from 2 to 5;
X is xe2x80x94NHxe2x80x94 or a covalent bond; 
in which R6 and R7 are independently selected from lower alkyl and lower alkanol; the solid and broken line denote a single or double covalent bond; R8 is selected from hydrogen, lower alkyl, xe2x80x94CO2R1, xe2x80x94(CH2)mR10, hydroxy, cyano, xe2x80x94(CH2)nNR11R12, wherein
m is zero or an integer from 1 to 3;
R10 is C3-7 cycloalkyl, naphthyl, and 
n is as above; and
with R13 being lower alkyl, lower alkenyl, C3-7 cycloalkyl, lower alkoxy, hydrogen, halogen, hydroxy, dialkylamino, phenoxy, amino, xe2x80x94NHCOR1, xe2x80x94CO2R1, NO2, trifluoromethyl, phenyl, and R11 and R12 are lower alkyl or are taken together as a C3-5 alkylene chain or an ethyl-oxy-ethyl chain.
These and other aspects of the invention will become apparent to one skilled in the art as described in the following detailed description.
The present invention is directed to novel compounds having NPYY1 antagonist activity and pharmaceutical compositions containing the novel compounds. The invention is further directed to a method of treating clinical disorders, such as eating disorders, using the novel compounds of the invention.
The compounds of the invention have the Formula I 
The compounds within the preview of the invention include the pharmaceutically acceptable acid addition salts and/or hydrates of the compounds of Formula I.
In the Formula I, R1 and R4 are independently selected from lower alkyl and CO2R5,
cyano and 
xe2x80x83where R5 is a lower alkyl;
R2 and R3 are independently selected from hydrogen, cyano and lower alkyl;
A is an alkyl or cycloalkyl;
X is xe2x80x94NHxe2x80x94 or a covalent bond;
n is an integer selected from 2 to 5; 
in which R6 and R7 are independently selected from lower alkyl and lower alkanol; the solid and broken line denote a single or double covalent bond; R8 is selected from hydrogen, lower alkyl, xe2x80x94CO2R1, xe2x80x94(CH2)mR10, hydroxy, cyano, xe2x80x94(CH2)nNR11R12, wherein
m is zero or an integer from 1 to 3; 
R10 is C3-7 cycloalkyl, naphthyl,
n is as above; and
with R13 being lower alkyl, lower alkenyl, C3-7 cycloalkyl, lower alkoxy, hydrogen, halogen, hydroxy, dialkylamino, phenoxy, amino, xe2x80x94NHCOR1, xe2x80x94CO2R1, NO2, trifluoromethyl, phenyl, and R11 and R12 are lower alkyl or are taken together as a C3-5 alkylene chain or an ethyl-oxy-ethyl chain.
The term xe2x80x9clowerxe2x80x9d refers to substituents such as alkyl or alkoxy groups that contain from one to four carbon atoms. Alkenyl groups generally contain two to four carbon atoms. In embodiments of the invention, R1 is preferably CO2R5 where R5 is methyl. R2 and R3 are preferably methyl. R5 is preferably C4R5 where R5 is methyl. A is preferably an C4H8 or cis-1,3-cyclophenyl. Z is preferably 4-(3-methoxyphenyl)-1-piperidinepropyl, 4-(cyclohexyl)-1-piperazinepropyl or 4-phenyl-1-piperazinepropyl.
The compounds of the present invention can exist as optical isomers and both the racemic mixtures of these isomers as well as the individual optical isomers themselves are within the scope of the present invention. The racemic mixtures can be separated into their individual isomers through well-known techniques such as the separation of the diastereomeric salts formed with optically active acids, followed by conversion back to the optically active bases.
As indicated, the present invention also pertains to the pharmaceutically acceptable non-toxic salts of these basic compounds. Such salts include those derived from organic and inorganic acids such as, without limitation, hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, methanesulfonic acid, acetic acid, dichloroacetic acid, tartaric acid, lactic acid, succinic acid, citric acid, maleic acid, fumaric acid, sorbic acid, aconitic acid, salicyclic acid, phthalic acid, enanthic acid, and the like.
The compounds of the invention can be produced by various processes that use variations of the Hantzsch synthetic reaction applied to the appropriate starting materials. The core 4-alkyl substituted dihydropyridines IIIa were prepared by standard Hantzsch condensation of the starting reactant IIa with methyl acetoacetate, methyl-3-aminocrotonate under reflux with isopropanol and ammonium acetate. The reaction scheme is as follows. 
The methyl ester group was saponified using 2N sodium hydroxide in water. The free acid was recovered by hydrochloric acid neutralization to produce the acid IVa 
The acids are then subjected to standard Curtius rearrangement with diphenyl phosphoryl azide at reflux in toluene to give the aliphatic isocyanate intermediates Va. Without further isolation, the reactive isocyanates Va were coupled with an amine with standard peptide coupling procedure using 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride (DEC) in 1,2-dichloroethane (DCE) or in N, N-dimethylformamide (DMF) at room temperature to give the compound of Formula I. The synthesis is according to the following scheme. 
The 4-cycloalkyl substituted dihydropyridines IIIb are prepared using the same Hantzsch condensation of the reactant IIb. The methyl ester group is saponified to produce the free acid, which is then subjected to Curtius rearrangement with diphenyl phosphoryl azide (DPPA) followed by coupling with an amine. The reaction scheme is as follows. 
(a) methyl acetoacetate and methyl 3-amino-crotonate in isopropanol
(b) 2N NaOH followed by HCl
(c) DPPA, Et3N in toluene at reflux quenched with NH2xe2x80x94(CH2)nZ
(d) DEC followed by NH2xe2x80x94(CH2)nZ.
The alkyl amines, such as the propanamines are produced by known processes. The amines can be produced from the appropriate secondary amines by conjugate addition to acrylonitrile in methanol. The reaction product is then hydrogenated catalytically in the presence of a Raney nickel catalyst in methanol to yield the amine as follows. 
a: acrylonitrile, MeOH, xcex94. b: H2, NH3, Raney Nickel, MeOH.
The alkyl piperazine can be synthesized using standard procedures by N-alkylation of the respective piperazine followed by removal of the Boc protecting groups as follows. 
The Boc protecting group can also be cleaved from the intermediate in methanol and HCl to produce the unsubstituted piperazine derivative as follows.
The compounds of the invention demonstrate binding affinity at NPY Y1 receptors. This pharmacologic activity is assayed in SK-N-MC (human neuroblastoma) cell membranes using iodine-125-labeled I-PYY as a radioligand. The compounds of Formula I had good binding affinities as evidenced by IC50 values being about 10 xcexcM or less at NPY Y1 receptors. Preferred compounds have IC50 values less than 100 nM and most preferred compounds have IC50 values of less than 10 nM. These types of dihydropyridines have significant affinity for xcex11-adrenergic receptors and/or Ca++ channels.
Pharmacologically, the compounds of Formula I act as selective NPY antagonists at NPY Y1 receptor sites. As such, the compounds of Formula I are of value in the treatment of a wide variety of clinical conditions which are characterized by the presence of an excess of neuropeptide Y. Thus, the invention provides methods for the treatment or prevention of a physiological disorder associated with an excess of neuropeptide Y, which method comprises administering to a mammal in need of treatment an effective amount of a compound of Formula I or a pharmaceutically acceptable salt, solvate or prodrug thereof. The term xe2x80x9cphysiological disorder associated with an excess of neuropeptide Yxe2x80x9d encompasses those disorders associated with an inappropriate stimulation of neuropeptide Y receptors, regardless of the actual amount of neuropeptide Y present in the locale.
These physiological disorders include:
disorders or diseases pertaining to the heart, blood vessels or the renal system, such as vasospasm, heart failure, shock, cardiac hypertrophy, increased blood pressure, angina, myocardial infarction, sudden cardiac death, congestive heart failure, arrhythmia, peripheral vascular disease, and abnormal renal conditions such as impaired flow of fluid, abnormal mass transport, or renal failure;
conditions related to increased sympathetic nerve activity for example, during or after coronary artery surgery, and operations and surgery in the gastrointestinal track;
cerebral diseases and diseases related to the central nervous system, such as cerebral infarction, neurodegeneration, epilepsy, stroke, and conditions related to stroke, cerebral vasospasm and hemorrhage, depression, anxiety, schizophrenia, dementia, seizure, and epilepsy;
conditions related to pain or nociception;
diseases related to abnormal gastrointestinal motility and secretion, such as different forms of ileus, urinary incontinence, and Crohn""s disease;
abnormal drink and food intake disorders, such as obesity, anorexia, bulemia, and metabolic disorders;
diseases related to sexual dysfunction and reproductive disorders such as benign prostatic hyperplasia and male erectile dysfunction;
conditions or disorders associated with inflammation;
respiratory diseases, such as asthma and conditions related to asthma and bronchoconstriction;
diseases related to abnormal hormone release, such as leutinizing hormone, growth hormone, insulin and prolactin; and
sleep disturbance and diabetes.
There is evidence that NPY contributes to certain symptoms in these disorders, such as, hypertension, eating disorders, and depression/anxiety, as well as circadian rhythms. Compounds of this invention are expected to be useful in treating these disorders as well as sleep disturbance and diabetes.
Selected compounds are tested further for their ability to block or stimulate NPY-induced feeding in test animals by intraperitoneal administration to the animal prior to inducing feeding behavior with NPY. Taken together, these tests indicate that the compounds of this invention would be useful anorexiants and would function as anti-obesity agents with further use in various clinical eating disorders. Thus, another aspect of the invention concerns a process for reducing food intake in an obese mammal or a mammal with an eating disorder. The process comprises systemic administration to such a mammal of an anorexiant-effective dose of a Formula I compound or a pharmaceutically acceptable acid addition salt and/or hydrate thereof.
On the basis of pharmacologic testing, an effective dose given parenterally could be expected to be in a range of about 0.05 to 1 mg/kg body weight and if given orally would be expected to be in the range of about 1 to 50 mg/kg body weight.
For clinical applications, however, the dosage and dosage regimen must in each case be carefully adjusted, utilizing sound professional judgment and considering the age, weight and condition of the recipient, the route of administration and the nature and gravity of the illness. Generally, the compounds of the instant invention will be administered in the same manner as for available anorexiant drugs such as Diethylpropion, Mazindol, or Phentermine and the daily oral dose would comprise from about 70 to about 1400 mg, preferably 500 to 1000 mg administered from 1 to 3 times a day. In some instances, a sufficient therapeutic effect can be obtained at lower doses while in others, larger doses will be required.
The term systemic administration as used herein refers to oral, buccal, transdermal, rectal, and parenteral (i.e. intramuscular, intravenous, and subcutaneous) routes. Generally, it will be found that when a compound of the present invention is administered orally, which is the preferred route, a larger quantity of reactive agent is required to produce the same effect as a smaller quantity given parenterally. In accordance with good clinical practice, it is preferred to administer the instant compounds at a concentration level that will produce effective anoretic effects without causing any harmful or untoward side effects. Similarly, the instant compounds can be administered to treat the various diseases, conditions, and disorders listed above.
Therapeutically, the compounds of Formula I are generally given as pharmaceutical compositions comprised of an effective anorectic amount of a compound of Formula I or a pharmaceutically acceptable acid addition salt thereof and a pharmaceutically acceptable carrier. Pharmaceutical compositions for effecting such treatment will contain a major or minor amount, e.g. from 95 to 0.5% of at least one compound of the present invention in combination with the pharmaceutical carrier. The carrier comprises one or more solid, semi-solid, or liquid diluent, filler, and formulation adjuvant that is non-toxic, inert and pharmaceutically acceptable.
Such pharmaceutical compositions are preferably in dosage unit forms; i.e., physically discrete units containing a predetermined amount of the drug corresponding to a fraction or multiple of the dose which is calculated to produce the desired therapeutic response. The dosage units can contain 1, 2, 3, 4, or more single doses, or, alternatively, one-half, one-third, or one-fourth of a single dose. A single dose preferably contains an amount sufficient to produce the desired therapeutic effect upon administration at one application of one or more dosage units according to the pre-determined dosage regimen usually a whole, half, third, or quarter of the daily dosage administered once, twice, three, or four times a day. Other therapeutic agents can also be present. Pharmaceutical compositions which provide from about 50 to 1000 mg of the active ingredient per unit dose are preferred and are conventionally prepared as tablets, lozenges, capsules, powders, transdermal patches, aqueous or oily suspensions, syrups, elixirs, and aqueous solutions. Preferred oral compositions are in the form of tablets or capsules and may contain conventional excipients such as binding agents (e.g. syrup, acacia, gelatin, sorbitol, tragecanth, or polyvinylpyrrolidone), fillers (e.g. lactose, sugar, maize-starch, calcium phosphate, sorbitol, or glycine), lubricants (e.g. magnesium stearate, talc, polyethylene glycol or silica), disintegrants (e.g. starch) and wetting agents (e.g. sodium lauryl sulfate).
Solutions or suspensions of a Formula I compound with conventional pharmaceutical vehicles are generally employed for parenteral compositions such as an aqueous solution for intravenous injection or an oily suspension for intramuscular injection. Such compositions having the desired clarity, stability and adaptability for parenteral use are obtained by dissolving from 0.1% to 10% by weight of the active compound in water or a vehicle consisting of a polyhydric aliphatic alcohol such as glycerine, propyleneglycol, and polyethylene glycols or mixtures thereof. The polyethyleneglycols consist of a mixture of non-volatile, usually liquid, polyethyleneglycols which are soluble in both water and organic liquids and which have molecular weights from about 200 to 1500.